Current day technology for displaying stereoscopic images by utilizing liquid crystal display panels includes a multi-layer display (MLD) type and a barrier type.
The Multi-layer display type can be further categorized into two types of applications. Please refer to FIG. 1, which illustrates the first type of application of the multi-layer display in the prior art. The first type of application is called a depth-fused display. In the depth-fused display, an image being displayed by a front liquid crystal display panel 100 is the same as an image displayed by a rear liquid crystal display panel 110, and brightness of the image displayed by the front liquid crystal display panel 100 is different from brightness of the image being displayed by the rear liquid crystal display panel 110 so as to show consecutive depth perception. For example, when the brightness of the image being displayed by the front liquid crystal display panel 100 is greater than the brightness of the image being displayed by the rear liquid crystal display panel 110, human eyes will see an image fusion near the front liquid crystal display panel 100, such as a circular graph A in the drawing. In contrast, when the brightness of the image being displayed by the rear liquid crystal display panel 110 is greater than the brightness of the image being displayed by the front liquid crystal display panel 100, human eyes will see the image fusion near the rear liquid crystal display panel 110, such as a circular graph B in the drawing. That is, by controlling the brightness of the image being displayed by the front liquid crystal display panel 100 and the brightness of the image displayed by the rear liquid crystal display panel 110, the image fusion may be shown at any depth between the front liquid crystal display panel 100 and the rear liquid crystal display panel 110 and the image fusion looks stereoscopic in such manner.
The second type of application (not shown) of the multi-layer display type is composed of a front liquid crystal display panel and a rear liquid crystal display panel as well. The difference between the depth-fused display and the second type of application is that an image being displayed by the front liquid crystal display panel of the second type of application is different from an image being displayed by the rear liquid crystal display panel thereof. The rear liquid crystal display panel usually displays a background image, and the front liquid crystal display panel displays a foreground image. The stereoscopic images with layering effect may be shown by displaying the foreground image different from the background image. The second type of application may be designed to use two polarizers or designed to use four polarizers. In the design using two polarizers, the two polarizers are disposed at the outer side of the front liquid crystal display panel and the outer side of the rear liquid crystal display panel, respectively. Brightness of an image being displayed by the front liquid crystal display panel has to be greater than brightness of an image being displayed by the rear liquid crystal display panel, because the image being displayed by the front liquid crystal display panel will cover the image being displayed by the rear liquid crystal display panel in human eyes. If the brightness of the image being displayed by the rear liquid crystal display panel is greater than brightness of an image being displayed by the front liquid crystal display panel, the image being displayed by the front liquid crystal display panel will fail to cover the image being displayed by the rear liquid crystal display panel so as to generate perspective perception in human eyes.
In the design using four polarizers, the four polarizers are disposed at the inner sides and the outer sides of the front liquid crystal display panel and the rear liquid crystal display panel, respectively. The arrangement of the brightness of an image being displayed by the front liquid crystal display panel and the brightness of an image being displayed by the rear liquid crystal display panel is contrary to the design using two polarizers. That is, the brightness of the image being displayed by the rear liquid crystal display panel has to be greater than brightness of the image being displayed by the front liquid crystal display panel, because the required lights of the front liquid crystal display panel are provided by the rear liquid crystal display panel. Among the aforementioned four polarizers, the two polarizers that are disposed at the inner sides of the front liquid crystal display panel and the rear liquid crystal display panel (i.e. the two polarizers between front liquid crystal display panel and the rear liquid crystal display panel) may be simplified as one polarizer. That is, only one of the polarizer being disposed at the inner side of the front liquid crystal display panel and the polarizer being disposed at the inner side of the rear liquid crystal display panel is chosen. The polarizer that is disposed at the outer side of the front liquid crystal display panel and the polarizer that is disposed at the outer side of the rear liquid crystal display panel remain unchanged. As a result, the design using four polarizers may be simplified as the design using three polarizers.
Please refer to FIG. 2, which illustrates the barrier type of the stereoscopic display technology in the prior art. A backlight module 200 provides lights required by a liquid crystal display panel 210. Firstly, images are observed from two different angles. Then, the images from two different angles are divided into vertical strips in equal distance, respectively. Finally, the vertical strips of one image are interlaced and merged as one image, and the merged image is displayed in the liquid crystal display panel 210. Odd strips 212 of the merged image are provided for a left eye 230, and even strips 214 of the merged image are provided for a right eye 240. Slits 222 of an optical grating 220 are utilized for limiting the left eye to observe only the odd strips 212 of the merged image. Barriers 224 of the optical grating 220 are utilized for limiting the right eye to observe only the even strips 214 of the merged image. As a result, the merged image looks stereoscopic due to binocular parallax. It is noted that a length of one of the slits 222 of the optical grating 220 in the horizontal direction has to be smaller than a length of a pixel of the liquid crystal display panel 210 in the horizontal direction. If the length of one of the slits 222 of the optical grating 220 in the horizontal direction is equal to or longer than the length of the pixel of the liquid crystal display panel 210 in the horizontal direction, the slits 222 and the barriers 224 will fail to limit the images that is observed by the left eye and the right eye. Accordingly, the left eye and the right eye will fail to generate binocular parallax and therefore the merged image will not look stereoscopic. Please refer to FIG. 3, which illustrates the barrier type utilizing two liquid crystal display panel 300, 310 in the prior art. The upper liquid crystal display panel 300 displays slits and barriers as shown in FIG. 2 by controlling indium tin oxide (ITO) electrodes 302, 304. That is, the upper liquid crystal display panel 300 displays black and white strips, and these strips are vertical. The slits are displayed as the white strips, and the barriers are displayed as the black strips so as to function as the optical grating 220 in FIG. 2. The lower liquid crystal display panel 310 is utilized for interlacing displayed images for the left eye and the right eye.
Although the multi-layer display type and the barrier type can be implemented by using two liquid crystal display panels, a stereoscopic display device can only implement either the multi-layer display type or the barrier type. Accordingly, such the stereoscopic display panel lack of flexibility in application. Therefore, there is a need for a solution to the above-mentioned problem that a stereoscopic display device cannot implement the multi-layer display type and the barrier type.